Vaporizer for cvd, solution voporizing cvd system and voporization method for cvd

ABSTRACT

The vaporizer for CVD of the present invention comprises: the pipes for the plurality of raw-material solutions, each pipe supplying the plurality of raw-material solutions separately from one another; the pipe for the carrier gas provided in a manner covering outwards of the pipes for the raw-material solutions, the pipe  3  allowing the pressurized carrier gas to flow thereinside and the outwards of the pipes for the raw-material solutions; the orifice provided on a leading end of the pipe for the carrier gas, the orifice being spaced away from leading ends of the pipes for the raw-materials solutions; the vaporizing tube connected to the leading end of the pipe for the carrier gas, the vaporizing tube being connected to the inside of the pipe for the carrier gas via the orifice; the cleaning mechanism cleaning at least one among the leading end of the pipe for the carrier gas, the orifice, and the vaporizing tube; and a heating means for heating the vaporizing tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vaporizer for CVD (Chemical VaporDeposition), a solution-vaporization type CVD apparatus and avaporization method for CVD. In particular, the present inventionrelates to a vaporizer for CVD, a vaporization method for CVD and asolution-vaporization type CVD apparatus including the vaporizer whichcan suppress a clogging at a solution pipe etc., for extendingcontinuous operation times thereof.

2. Description of the Related Art

In a technique of CVD applied to semiconductor industry from around1970, when forming a thin film, a reactant in gas state is introducedinto a reactor, allowed to react, and thus a thin film of variouscompositions is formed on a semiconductor substrate made of, forinstance, silicon. With respect to the CVD technique, however, there isa technical limitation that a thin film can not be formed by CVD unlessa gas reactant is prepared.

At IEDM (International Electron Devices Meeting) of 1987, W. I. KINNEYet al. announced a technique for fabricating a ferroelectric memoryFeRAM (FRAM: Ferroelectric Random Access Memory) by utilizing apolarization phenomenon of a ferroelectric material such as PZT, SBT. Atthat time, a thin film of a ferroelectric material such as PZT, SBTcould not be formed by CVD because it was technically difficult toprepare a chemical in a gas state containing Zr, Sr, Bi or the like.Accordingly, a solution coating process, similar to one for forming aphoto resist was applied to the fabrication of a FeRAM. A ferroelectricthin film (thickness: 400-300 nm) formed by the solution coatingprocess, however, has poor step coverage. Moreover, when it is thinned(thickness: 150-40 nm), the number of pin holes are increased, wherebyelectrical isolation thereof is decreased. Because a FeRAM-LSI has aplurality of steps and requires the thinning of a ferroelectric material(thickness: 100-50 nm), it is necessary that a high-qualityferroelectric thin film be formed by CVD in order to attempt to put aFeRAM-LSI to practical use.

In 1992, Dr. Shiozaki, an assistant professor in the engineering Dept.at Kyoto University, formed a ferroelectric thin film PZT by CVD andannounced this formation at an academic conference. A CVD apparatus usedby Dr. Shiozaki adopted a technique for vaporizing (gasifying) a solidchemical by sublimation.

In the technique for gasifying a solid chemical by sublimation, however,it is difficult to increase a flow rate of a reactant because a rate ofsublimation when sublimating a solid chemical is low. Moreover, becauseof the difficulty of the controlling the flow rate of the reactant, adeposition rate of a thin film is low, thus resulting in a poorreproducibility. Further, it is difficult to carry the sublimatedchemical to a reactor with a pipe heated at approximately 250° C.

In order to make an additional experiment on the technique announced byDr. Shiozaki, the inventor of the present invention purchased the sameCVD apparatus used by Dr. Shiozaki from the same manufacturer with Dr.Shiozaki's assistance, and performed a film-forming experiment.Immediately after starting an operation of the CVD apparatus, however, ahigh-temperature pipe was clogged. After fixed, the high-temperaturepipe was then heated extraordinary. Based on his experience like this,he concluded that a technique for evenly heating thin, longstainless-made pipes (external diameter: ¼ inch and length: 1 m ofseveral pipes) with a plurality of valves on middle portions thereof at250±5° C. is an extremely difficult technique.

Based on the above-described experience, he reached to a thought that itis difficult to put the sublimation-type CVD apparatus to practical use.Consequently, he successfully deposited a high-quality thin film of aferroelectric material SBT by solution-vaporization CVD (so-called“flash CVD”). He announced it at an international academic conference,ISIF '96 (“Performance of SrBi₂Ta₂O₉ Thin Films Grown by Chemical VaporDeposition for Nonvolatile Memory Applications”. C. Isobe, H. Yamoto, H.Yagi et al. 9^(th) International Symposium on Integrated Ferroelectrics.March, 1996), and verified the possibility of the commercialization of aferroelectric memory FeRAM.

As a vaporizer for producing a reaction gas for SBT-thin-film-formationby dissolving solid material in solvent so as to produce solution, andallowing the solution to gasify at high temperature, one made by ATMIInc. was initially adopted. This vaporizer, however, was not adopted bya CVD apparatus of mass production type because it was clogged in amatter of ten hours. Consequently, in 1996, the inventor of the presentinvention Mr. Yoshioka of Shimadzu Corporation and Dr. Toda, a professorof Material Engineering dept. of Faculty of Engineering at YamagataUniversity to develop and manufacture a high-performance solutionsupplying system and a vaporizer necessary for stably depositing ahigh-quality SBT thin film. An apparatus (the solution supplying systemand vaporizer) delivered to him, however, had the following technicalproblem, and thus it was difficult to stably deposit a SBT thin film.Meanwhile, this apparatus is disclosed by Japanese Unexamined PatentPublications No. 2000-216150 and No. 2002-105646.

As a reactant for synthesizing a SBT thin film, Sr(DPM)₂, BiPh₃,Ta(OEt)₅, Sr[Ta(OEt)₅(OC₂H₄OMe)]₂, Bi(OtAm)₃, Bi(MMP)₃, etc. are usedparticularly, when Sr[Ta(OEt)₅(OC₂H₄OMe)]₂+Bi(MMP)₃ is used, ahigh-speed deposition (5-100 nm/min) at 320-420° C. can be performed,whereby a high-quality SBT thin film having good step coverage andelectrical property can be formed. The above apparatus, however, wasclogged immediately when Sr[Ta(OEt)₅(OC₂H₄OMe)]₂+Bi(MMP)₃ was used as areactive gas. The inventor of the present invention researched andexamined the reason thereof, and found that when solutions ofSr[Ta(OEt)₅(OC₂H₄OMe)]₂ and Bi(MMP)₃ were mixed at room temperature,Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ and Bi(MMP)₃ reacted with each other, a materialhaving a small solubility and not easily subliming was synthesized bythe reaction, and thus a path for allowing the solutions to flow and aleading end of a vaporizing tube were clogged. This phenomenon will nowbe explained in detail.

FIG. 11 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) ofSr[Ta(OEt)₅(OC₂H₄OMe)]₂. This figure illustrates: a graph 101representing changes in a weight of a sample of Sr[Ta(OEt)₅(OC₂H₄OMe)]₂when the sample is subject to a temperature rising from 30 to 600° C. ata rate of 10° C./min. under argon atmosphere at a pressure of 760 Torrand a flow rate of 100 ml/min.; a graph 102 representing changes in aweight of the sample when it is subject to a temperature rising from 30to 600° C. at a rate of 10° C./min. under argon atmosphere at a pressureof 10 Torr and a flow rate of 50 ml/min.; and a graph 103 representingchanges in a weight of the sample when it is subject to a temperaturerising from 30 to 600° C. at a rate of 10° C./min. under oxygenatmosphere at a pressure of 760 Torr and a flow rate of 100 ml/min. Asis illustrated in the figure, Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ completelysublimes at approximately 220° C. under argon atmosphere at a pressureof 10 Torr.

FIG. 12 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of Bi(OtAm)₃. Thisfigure illustrates: a graph 111 representing changes in a weight of asample of Bi(OtAm)₃ when the sample is subject to a temperature risingfrom 30 to 600° C. at a rate of 10° C./min. under argon atmosphere at apressure of 760 Torr and a flow rate of 100 ml/min.; a graph 112representing changes in a weight of the sample when it is subject to atemperature rising from 30 to 600° C. at a rate of 10° C./min. underargon atmosphere at a pressure of 10 Torr and a flow rate of 50 ml/min.;and a graph 113 representing changes in a weight of the sample when itis subject to a temperature rising from 30 to 600° C. at a rate of 10°C./min. under oxygen atmosphere at a pressure of 760 Torr and a flowrate of 100 ml/min. As illustrated, approximately 98% of Bi(OtAm)₃sublimes at approximately 130° C. under argon atmosphere at a pressureof 10 Torr.

FIG. 13 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of Bi(MMP)₃. Thisfigure illustrates: a graph 121 representing changes in a weight of asample of Bi(MMP)₃ when the sample is subject to a temperature risingfrom 30 to 600° C. at a rate of 10° C./min. under argon atmosphere at apressure of 760 Torr and a flow rate of 100 ml/min.; a graph 122representing changes in a weight of the sample when it is subject to atemperature rising from 30 to 600° C. at a rate of 10° C./min. underargon atmosphere at a pressure of 10 Torr and a flow rate of 50 ml/min.;and a graph 123 representing changes in a weight of the sample when itis subject to a temperature rising from 30 to 600° C. at a rate of 10°C./min. under oxygen atmosphere at a pressure of 760 Torr and a flowrate of 100 ml/min. As illustrated, Bi(MMP)₃ completely sublimes atapproximately 150° C. under argon atmosphere at a pressure of 10 Torr.

FIG. 14 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of a mixture ofBi(OtAm)₃/Sr[Ta(OEt)₆]₂. This figure illustrates: a graph 131representing changes in a weight of a sample of Bi(OtAm)₃/Sr[Ta(OEt)₆]₂when the sample is subject to a temperature rising from 30 to 600° C. ata rate of 10° C./min. under argon atmosphere at a pressure of 760 Torrand a flow rate of 100 ml/min.; and a graph 133 representing changes ina weight of the sample when it is subject to a temperature rising from30 to 600° C. at a rate of 10° C./min. under oxygen atmosphere at apressure of 760 Torr and a flow rate of 100 ml/min. As illustrated, only80% of the mixture of Bi(OtAm)₃/Sr[Ta(OEt)₆]₂ sublimes under argonatmosphere even if it is heated at greater than or equal to 300° C.

As explained, both Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ and Bi(OtAm)₃ almostcompletely sublime in individuals, but when mixed with each other, partof them do not sublime. A deterioration of the sublimationcharacteristic thereof may cause the clogging of the vaporizer.

A reason for the deterioration of the sublimation characteristic can beexplained with NMR characteristic (Nuclear Magnetic Resonance of H) asillustrated in FIG. 15. When Bi(OtAm)₃ and Sr[Ta(OEt)₆]₂ are mixed, anew NMR characteristic is observed. This represents that a new chemicalcompound is formed and resides.

FIG. 16 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of a mixture ofBi(MMP)₃/Sr[Ta(OEt)₅(OC₂H₄OMe)]₂. This figure illustrates a graphrepresenting changes in a weight of a sample ofBi(MMP)₃/Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ when the sample is subject to atemperature rising from 30 to 600° C. at a rate of 10° C./min. underargon atmosphere at a pressure of 760 Torr and a flow rate of 100ml/min. As illustrated, only 80% of the mixture ofBi(MMP)₃/Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ sublimes under argon atmosphere.

FIG. 17 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of BiPh₃. Thisfigure illustrates: a graph 141 representing changes in a weight of asample of BiPh₃ when the sample is subject to a temperature rising from30 to 600° C. at a rate of 10° C./min. under argon atmosphere at apressure of 760 Torr and a flow rate of 100 ml/min.; a graph 142representing changes in a weight of the sample when it is subject to atemperature rising from 30 to 600° C. at a rate of 10° C./min. underargon atmosphere at a pressure of 10 Torr and a flow rate of 50 ml/min.;and a graph 143 representing changes in a weight of the sample when itis subject to a temperature rising from 30 to 600° C. at a rate of 10°C./min. under oxygen atmosphere at a pressure of 760 Torr and a flowrate of 100 ml/min. As illustrated, 100% of BiPh₃ sublimes atapproximately 200° C.

FIG. 18 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) ofBiPh₃/Sr[Ta(OEt)₆]₂. This figure illustrates: a graph 151 representingchanges in a weight of a sample of BiPh₃/Sr[Ta(OEt)₆]₂ when the sampleis subject to a temperature rising from 30 to 600° C. at a rate of 10°C./min. under argon atmosphere at a pressure of 760 Torr and a flow rateof 100 ml/min.; and a graph 153 representing changes in a weight of thesample when it is subject to a temperature rising from 30 to 600° C. ata rate of 10° C./min. under oxygen atmosphere at a pressure of 760 Torrand a flow rate of 100 ml/min. As illustrated, almost 100% ofBiPh₃/Sr[Ta(OEt)₆]₂ sublimes at approximately 280° C.

FIG. 19 illustrates NMR characteristics representing stability of mixingBiPh₃ and Sr[Ta(OEt)₆]₂. No synthesis of a new material is observed in amixture of BiPh₃/Sr[Ta(OEt)₆]₂.

FIG. 20 is a TG-DTA CHART (O₂ 760 Torr) of BiPh₃. As illustrated, anoxidation reaction of BiPh₃ occurs at 465° C. The oxidizing temperatureof BiPh₃ is so high with respect to 259° C. of Sr[Ta(OEt)₅(OC₂H₄OMe)]₂,209° C. of Bi(MMP)₃, and 205° C. of Bi(OtAm)₃, it is thus difficult touse BiPh₃.

Bi(OtAm)₃ causes a hydrolysis reaction with only 180 ppm of moisture.This means that Bi(OtAm)₃ is remarkably more sensitive to moisture thanSr[Ta(OEt)₅(OC₂H₄OMe)]₂ causing a hydrolysis reaction with 1650 ppm ofmoisture, and Bi(MMP)₃ causing that reaction with 170 ppm of moisture,and thus the treatment of Bi(OtAm)₃ is difficult. Since moisturecertainly exists, Bi(OtAm)₃ may be allowed to react with moisture toform Bi oxide, while a possibility that a pipe, a flow meter, etc. areclogged by the formed Bi oxide may increase.

The problems described above can be summarized as follows.

In the technique for vaporizing a solid chemical by sublimation at aroom temperature and for using this gas as a reactive gas, a depositionrate of thin film is low and varies, whereby it may be difficult to putit in practical use.

In contrast, in the solution-vaporization CVD using a solid chemical ata room temperature, dissolving the solid chemical in a solvent,atomizing it, and then vaporizing it at high temperature, a depositionrate of thin film is high. In this technique, however, there is aphenomenon that a chemical reaction occurs in a solution state, and thusa solution pipe or the like is clogged. When the solution-pipe or thelike is clogged, the CVD apparatus can be continuously operated forshort times. Therefore, it is necessary that a solution supplying systembe devised.

The present invention has been made to solve the above problems. It is,accordingly, an object of the present invention to provide a vaporizerfor CVD, a solution-vaporization type CVD apparatus, and a vaporizationmethod for CVD which can suppress a clogging at a solution pipe etc., soas to extend continuous operation times thereof.

SUMMARY OF THE INVENTION

In order to attain the above object, according to a first aspect of thepresent invention, there is provided a vaporizer for CVD whichcomprises: a dispersing portion dispersing a plurality of raw-materialsolutions in a carrier gas in fine particulate or misty forms; aplurality of paths for the plurality of raw-material solutions, each ofthe plurality of paths supplying the plurality of raw-material solutionsto the dispersing portion separately from one another; a path for thecarrier gas, the path supplying the carrier gas to the dispersingportion separately from the plurality of raw-material solutions; avaporizing member vaporizing the plurality of raw-material solutionsdispersed by the dispersing portion; an orifice connected to thevaporizing member and the dispersing portion, the orifice introducingthe plurality of raw-material solutions dispersed by the dispersingportion into the vaporizing member; and a cleaning mechanism cleaning atleast one of the dispersing portion, the orifice and the vaporizingmember.

According to the above-described vaporizer, since it has the cleaningmechanism, at least one of followings can be cleaned: the dispersingportion; the orifice; and the vaporizing member. When the vaporizationof the plurality of raw-material solutions are continuously carried out,solutes of the raw-material solutions gradually precipitate on at leastone of the dispersing portion, the orifice and the vaporizing tube, andthus the orifice is gradually clogged. However, by cleaning at least oneof them, the clogging can be eliminated.

Alternatively, the above described vaporizer may further comprise amonitoring mechanism for monitoring a pressure of the carrier gas. Byobserving the pressure thereof with the monitoring mechanism, thecondition of the clogging of the orifice can be observed. Accordingly aproper timing for cleaning at least one of the dispersing portion, theorifice and the vaporizing tube can be determined.

In order to attain the above object, according to a second aspect of thepresent invention, there is provided a vaporizer for CVD whichcomprises: a dispersing portion dispersing a plurality of raw-materialsolutions in a carrier gas in fine particulate or misty forms; aplurality of paths for the plurality of raw-material solutions, each ofthe plurality of paths supplying the plurality of raw-material solutionsto the dispersing portion separately from one another; a path for thecarrier gas, the path supplying the carrier gas to the dispersingportion separately from the plurality of raw-material solutions; amonitoring mechanism for monitoring a pressure of the carrier gas; avaporizing member vaporizing the plurality of raw-material solutionsdispersed by the dispersing portion; and an orifice connected to thevaporizing member and the dispersing portion, the orifice introducingthe plurality of raw-material solutions dispersed by the dispersingportion into the vaporizing member.

In the above-described vaporizer, it is preferable that the dispersingportion be arranged in between the orifice and respective leading endsof the plurality of paths, and the orifice have a smaller diameter thanthose of the plurality of the paths and the path for the carrier gas.

Moreover, in the above-described vaporizer, it is preferable that thevaporizing member be brought into a reduced pressure state and thedispersing portion be brought into an increased pressure state when theplurality of raw-material solutions vaporized.

In order to attain the above object, according to a third aspect of thepresent invention, there is provided a vaporizer for CVD whichcomprises: a plurality of pipes for a plurality of raw-materialsolutions, each of the plurality of pipes supplying the plurality ofraw-material solutions separately from one another; a pipe for a carriergas, the pipe being provided in a manner covering outwards of theplurality of pipes, while the pipe allowing the pressurized carrier gasto flow thereinside and the outward of each of the plurality of pipes;an orifice provided on a leading end of the pipe for the carrier gas,the orifice being spaced away from leading ends of the plurality ofpipes for the plurality of raw-material solutions; a vaporizing tubeconnected to the leading end of the pipe for the carrier gas, thevaporizing tube being connected to the inside of the pipe for thecarrier gas via the orifice; a cleaning mechanism cleaning at least onethe leading end of the pipe for the carrier gas, the orifice, thevaporizing tube and a heating means for heating the vaporizing tube.

According to the above-described vaporizer, since it has the cleaningmechanism, at least one of the followings can be cleaned: the leadingend of the pipe for the carrier gas; the orifice; and the vaporizingtube. When the vaporization of the plurality of raw-material solutionsare continuously carried out, solutes of the raw-material solutionsgradually precipitate on at least one of the leading end of the pipe forthe carrier gas, the orifice and the vaporization tube, and thus theorifice is gradually clogged. However, by cleaning at least one of them,the clogging can be eliminated.

Alternatively, the above-described vaporizer may further comprise amonitoring mechanism for monitoring a pressure of the carrier gas in theinside of the pipe for the carrier gas. By observing the pressurethereof with the monitoring mechanism, the condition of the clogging ofthe orifice can be observed. Accordingly a proper timing for cleaningcan be determined.

Moreover, in the above-described vaporizer, the cleaning mechanism mayclean the leading end of the pipe for the carrier gas and the orifice bysupplying at least one solution thereto.

In the above-described vaporizer, the carrier gas and the plurality ofraw-material solutions are mixed in between the orifice in the pipe forthe carrier gas and respective leading ends of the plurality of pipes,the plurality of raw-material solutions are dispersed in the carrier gasin fine particulate or misty forms, the plurality of dispersedraw-material solutions in fine particulate or misty forms are introducedinto the vaporizing tube via the orifice and heated by the heater so asto be vaporized. Accordingly, it is suppressed that only the solvents ofthe plurality of raw-material solutions vaporize at the orifice and thevaporizing tube adjacent to the orifice, and thus the chemical reactionof the plurality of raw-material solutions can be suppressed, wherebythe clogging can be suppressed.

In the above-described vaporizer, it is preferable that the orifice havea smaller diameter than those of the plurality of the pipes and the pipefor the carrier gas.

Moreover, in the above-described vaporizer, the plurality ofraw-material solutions can be one made by mixing Sr[Ta(OEt)₅(OC₂H₄OMe)]₂and a solvent, and one made by mixing Bi(MMP)₃ and a solvent, while thecarrier gas can be argon or nitrogen gas.

In order to attain the above object, according to a fourth aspect of thepresent invention, there is provided a solution-vaporization CVDapparatus which comprises one of the above-identified vaporizer for CVD.

In order to attain the above object, according to a fifth aspect of thepresent invention, there is provided a solution-vaporization CVDapparatus which comprises at least one vaporizer for CVD abovedescribed, and a reaction chamber being connected to the vaporizer,wherein a deposition is carried out with the plurality of raw-materialsolutions used, the plurality of raw-material solutions being vaporizedby the vaporizing tube.

Alternatively, in the above-described solution-vaporization CVDapparatus, it may be equipped with the plurality of vaporizers for CVD;some of the plurality of vaporizers for CVD may be respectively in acleaned condition cleaned by the cleaning mechanism, while othersthereof may be respectively in operated condition; and the plurality ofvaporized raw-material solutions may be continuously supplied to thereaction chamber by swapping the plurality of vaporizers for CVD in theoperated conditions for those in the cleaned conditions as timeadvances.

In order to attain the above object, according to a sixth aspect, thereis provided a vaporization method for CVD which comprises processes of:supplying a plurality of raw-material solutions and a carrier gas to adispersing portion separately from one another; mixing the plurality ofraw-material solutions and the carrier gas by the dispersing portion anddispersing the plurality of raw-material solutions in the carrier gas infine particulate or misty forms; vaporizing the raw-material solutionsby adiabatic expansion immediately after dispersing; and cleaning atleast one of the dispersing portion and an area for vaporizing theraw-material solutions.

In order to attain the above object, according to a seventh aspect ofthe present invention, there is provided a vaporization method for CVDwhich comprises processes of: supplying a plurality of raw-materialsolutions and a carrier gas to a dispersing portion separately from oneanother; mixing the plurality of raw-material solutions and the carriergas by the dispersing portion, and dispersing the plurality ofraw-material solutions in the carrier gas in fine particulate or mistyforms; vaporizing the raw-material solutions by adiabatic expansionimmediately after dispersing; observing a pressure of the carrier gaswhile vaporizing the raw-material solutions, and terminating the supplyof the raw-material solutions to the dispersing portion upon observingthat the pressure of the carrier gas exceeds a predetermined value; andcleaning at least one of the dispersing portion and an area forvaporizing the plurality of raw-material solutions.

Alternatively, in the above-described vaporization method for CVD, theprocess for cleaning may be one for cleaning at least one of thedispersing portion and the area for vaporizing the plurality ofraw-material solutions by supplying a solvent and the carrier gasthereto; and the pressure of the carrier gas may be monitored during theprocess for cleaning so that the supply of the solvent is terminatedupon observing that the pressure of the carrier gas is turned less thanor equal to the predetermined value so as to terminate the process forcleaning.

Moreover, in the above-described vaporization method for CVD, thesolvent for cleaning and solvents contained in the plurality ofraw-material solutions may be homogeneous.

Further, in the above-described vaporization method for CVD, the solventfor cleaning may be one or a mixture of those selected from a groupconsisting of ethyl cyclohexane, n-hexane, benzene, toluene, octane, ordecane.

According to the present invention, there are provided a vaporizer forCVD, a solution-vaporization CVD apparatus, and a vaporization methodfor CVD which can suppress a clogging at a solution-pipe etc., so as toextend continuous operation times thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view illustrating a structure of a solutionsupplying system included in a vaporizer for CVD according to a firstembodiment of the present, invention, while FIG. 1B is a schematic crosssectional view illustrating the solution supplying system of thevaporizer, a dispersing portion thereof, and a vaporizing memberthereof;

FIG. 2C is a schematic view illustrating a structure of a solutionsupplying system included in a vaporizer for CVD according to a secondembodiment of the present invention, while FIG. 2D is a schematic viewillustrating a structure of a solution supplying system included in avaporizer for CVD according to a third embodiment of the presentinvention;

FIG. 3 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 4 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 5 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 6 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 7 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 8 is a view illustrating an experimental result that pressures of acarrier gas were monitored;

FIG. 9 is a view illustrating a result of an experiment ofreproducibility of SBT-CVD with the vaporizer according to the firstembodiment;

FIG. 10 is a view illustrating the result of the experiment ofreproducibility of SBT-CVD with the vaporizer according to the firstembodiment;

FIG. 11 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) ofSr[Ta(OEt)₅(OC₂H₄OMe)]₂;

FIG. 12 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of Bi(OtAm)₃;

FIG. 13 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of Bi(MMP)₃;

FIG. 14 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of a mixture ofBi(OtAm)₃/Sr[Ta(OEt)₆]₂;

FIG. 15 a view illustrating NMR characteristic (nuclear magneticresonance of H);

FIG. 16 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of a mixture ofBi(MMP)₃/Sr[Ta(OEt)₅(OC₂H₄OMe)]₂;

FIG. 17 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) of BiPh₃;

FIG. 18 is a TG CHART (Ar 760/10 Torr, O₂ 760 Toor) ofBiPh₃/Sr[Ta(OEt)₆]₂;

FIG. 19 is a view illustrating NMR characteristics representingstability of mixing BiPh₃ and Sr[Ta(OEt)₆]₂; and

FIG. 20 is TG-DTA CHART (O₂ 760 Torr) of BiPh₃.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the accompanying drawings.

First Embodiment

FIG. 1A is a schematic view illustrating a structure of a solutionsupplying system included in a vaporizer for CVD according to a firstembodiment of the present invention, while FIG. 1B is a schematic crosssectional view illustrating the solution supplying system of thevaporizer, a dispersing portion thereof, and a vaporizing memberthereof.

As illustrated in FIGS. 1A and 1B, the vaporizer for CVD has first andsecond pipes 1, 2 for raw-material solutions. The first pipe 1 isprovided adjacent to the second pipe 2 in parallel therewith. A pipe 3for a carrier gas is provided outwardly relative to the first and secondpipes 1, 2. An internal diameter of the pipe 3 is formed to be largerthan a sum of an external diameter of the first pipe 1 and that of thesecond pipe 2. The first and second pipes 1, 2 are inserted into theinside of the pipe 3, while the pipe 3 is formed in a manner containingthe first and second pipes 1, 2 thereinside.

A base end of the first pipe 1 is connected to a first supplyingmechanism 4 for supplying a chemical 1 and a solvent. The firstsupplying mechanism 4 has a chemical-supplying-source for supplying thechemical 1 (for instance, Sr[Ta(OEt)₅(OC₂H₄OMe)]₂), and asolvent-supplying-source for supplying the solvent. A valve 6 and amass-flow controller (not illustrated) are provided in between thechemical-supplying-source and the first pipe 1. Moreover, a valve 7 anda mass-flow controller (not illustrated) are provided in between thesolvent-supplying-source and the first pipe 1. The solvent and thechemical 1 flow into each other (mix) in between thesolvent-supplying-source and the first pipe 1.

A base end of the second pipe 2 is connected to a second supplyingmechanism 5 for supplying a chemical 2 and a solvent. The secondsupplying mechanism 5 has a chemical-supplying-source for supplying thechemical 2 (for instance, Bi(MMP)₃), and a solvent-supplying-source forsupplying the solvent. A valve 8 and a mass-flow controller (notillustrated) are provided in between the chemical-supplying-source andthe second pipe 2. Moreover, a valve 9 and a mass-flow controller (notillustrated) are provided in between the solvent-supplying-source andthe second pipe 2. The solvent and the chemical 2 flow into each other(mix) in between the solvent-supplying-source and the second pipe 2.

A base end of the pipe 3 is connected to a third supplying mechanism 12for supplying an argon gas and a nitrogen gas. The third supplyingmechanism 12 has an argon-gas-supplying-source for supplying the argongas (Ar), and a nitrogen-gas-supplying-source for supplying thenitrogen-gas (N₂). A valve 10 and a mass-flow controller (notillustrated) are provided in between the argon-gas-supplying-source andthe pipe 3. Moreover, a valve 11 and a mass-flow controller (notillustrated) are provided in between the nitrogen-gas-supplying-sourceand the pipe 3. A high-precision pressure gauge 17 is provided inbetween the third supplying mechanism 12 and the pipe 3, while thehigh-precision pressure gauge 17 is one for constantly monitoring apressure of the carrier gas in the inside of the pipe 3. Thehigh-precision pressure gauge 17 sends an output signal to anon-illustrated controller. Based on the output signal, the pressure ofthe carrier gas can be displayed by a non-illustrated control-monitorand monitored.

A leading end of the pipe 3 is connected to one end of a vaporizing tube13. An orifice is formed on the leading end of the pipe 3, while itallows the inside of the pipe 3 and that of the vaporizing tube 13 to beconnected with each other. A heater is provided around the vaporizingtube 13, while the vaporizing tube 13 is heated at, for instance, 270°C. by the heater. The other end of the vaporizing tube 13 is connectedto a non-illustrated reaction chamber.

Leading ends of the first and second pipes 1, 2 are spaced away from theorifice, respectively. A dispersing portion 14 is formed in between therespective leading ends of the first and second pipes 1, 2 in the insideof the pipe 3 and the orifice. The dispersing portion 14 mixes: a firstraw-material solution (one made by mixing the chemical 1 and the solventthereof) flows out of the leading end of the first pipe 1; a secondraw-material solution (one made by mixing the chemical 2 and the solventthereof) flows out of the leading end of the second pipe 2; and theargon or nitrogen gas flows out of the pipe 3, and then disperses thefirst and second raw-material solutions in the argon or nitrogen gas infine particulate or misty forms.

Next, operations of the above vaporizer for CVD will now be explained indetail.

First, the valve 6 is opened so as to supply the first raw-materialsolution from the first supplying mechanism 4 to the first pipe 1 atpredetermined flow rate and pressure. The first raw-material solutionis, for instance, one made by mixing Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ and thesolvent thereof. Moreover, the valve 8 is opened so as to supply thesecond raw-material solution from the second supplying mechanism 5 tothe second pipe 2 at predetermined flow rate and pressure. The secondraw-material solution is, for instance, one made by mixing Bi(MMP)₃ andthe solvent thereof. Further, the valves 10, 11 are opened so as tosupply the carrier gas from the third supplying mechanism 12 to the pipe3 at predetermined flow rate and pressure. The carrier gas is, forinstance, the argon or nitrogen gas.

Next, the first raw-material solution is supplied to the dispersingportion 14 via the first pipe 1, the second raw-material solution isalso supplied to the dispersing portion 14 via the second pipe 2, whilethe pressurized carrier gas is supplied to the dispersing portion 14 viathe pipe 3. The dispersing portion 14 mixes the first raw-materialsolution, the second raw-material solution and the carrier gas, while itdisperses the first and second raw-material solutions in the carrier gasin fine particulate or misty forms. It is preferable that the first andsecond raw-material solutions mixed by the dispersing portion 14 bedispersed in fine particulate or misty forms within a single second.

The first and second raw-material solutions dispersed in the carrier gasby the dispersing portion 14 are introduced into the vaporizing tube 13via the orifice. In the vaporizing tube 13, the first and secondraw-material solutions dispersed in misty forms are instantaneouslyheated at approximately 270° C. by the heater.

There is a large difference between a pressure of the inside of thedispersing portion 14 and that of the inside of the vaporizing tube 13.The inside of the vaporizing portion 13 is in a reduced pressurecondition, while the dispersing portion 14 is in an increased pressurecondition. The pressure of the inside of the vaporizing portion 13 is,for instance, 5-30 Torr, while that of the inside of the dispersingportion 14 is, for instance, 1500-2200 Torr. By setting thepressure-difference like this, the carrier gas is ejected toward thevaporizing tube 13 at ultrahigh-speed, and expands (for instance,adiabatic expansion) in accordance with the pressure-difference.Accordingly, a sublimation temperature of chemicals contained in thefirst and second raw-material solutions is dropped, and thus theraw-material solutions (with the chemicals) can be vaporized by the heatfrom the heater. Moreover, the first and second raw-material solutionsare turned to be fine mist by the high-speed flow of the carrier gasimmediately after dispersed by the dispersing portion 14, and thus theyare easily vaporized instantaneously.

Thus way, a source gas is produced by vaporizing the first and secondraw-material solutions in the vaporizer for CVD. The source gas isintroduced into a reaction chamber via the vaporizing tube 13, while athin film is deposited on a substrate to be processed by CVD.

As mentioned above, while vaporizing the raw-material solutions, thepressure of the carrier gas is constantly monitored by thehigh-precision pressure gauge 17. When the vaporizer for CVD iscontinuously operated, solutes of the raw-material solutions graduallyprecipitate on at least one of the dispersing portion 14 and theorifice, and thus the orifice (atomizing nozzle) is gradually clogged.The phenomenon is as follow.

When Sr[TA(OEt)₅(OC₂H₄OMe)]₂, Bi(MMP)₃, solutions (for instance, EthylCycloHexane:ECH) and the carrier gas (for instance, argon, nitrogen) aresprayed to the high-temperature vaporizing tube 13 underreduced-pressure atmosphere (approximately 5-30 Torr) so as to beatomized, some of the mist adhere to the atomizing nozzle and liquefy.In a solution adhering to the atomizing nozzle, only a solvent (forinstance, Ethyl CycloHexane:ECH) having large vapor pressure isevaporated due to reduced-pressure atmosphere and the heat radiated fromthe vaporizing tube 13 in a high-temperature condition, solutesprecipitate, and thus the atomizing nozzle is clogged.

As the clogging progressing, the pressure of the carrier gas in theinside of the pipe 3 increases. After the controller is notified by thehigh-precision pressure gauge 17 that the pressure of the carrier gasexceeds the predetermined value (for instance, 200 KPa) by receiving anoutput signal therefrom, the valves 6, 8 are closed so as to terminatethe supply of the solutions of Sr[TA(OEt)₅(OC₂H₄OMe)]₂ and Bi(MMP)₃,while the valves 7, 9 are opened so as to allow only the solvents toflow. Or, an outlet of the vaporizing tube 13 is changed from a reactorto an exhaust portion (not illustrated), the solutions and the carriergas are only supplied to the pipes 1 to 3 for cleaning. By increasingthe volume of the flow of the solvents twice to ten times as much asthat of the solutions, an effectiveness of the cleaning can be improved.Accordingly, the atomizing nozzle sprays the solvents, while the solutesprecipitating thereon are re-dissolved by the solvents, whereby they areeliminated therefrom. Meanwhile, in this embodiment, the solvents forthe cleaning are supplied from the first and second supplyingmechanisms, but the supply thereof is not limited to this. For instance,a solvent supplying mechanism for the cleaning may be separatelyprovided, while a solvent for the cleaning may be supplied from thissolvent supplying mechanism. Moreover, it is preferable that thesubstrate to be processed be taken out from the reaction chamber priorto the cleaning, while a new substrate to be processed be put into thereaction chamber after the cleaning. When the solutes precipitate andadhere to the dispersing portion 14 or the like, lowering thesublimation rate of a CVD thin film and the change of the compositionthereof are observed. As a result, a reproducibility of theCVD-thin-film deposition process, the quality thereof and the yieldthereof are lowered. To prevent those lowering, it is preferable thatthe cleaning be carried out prior to the detection of the clogging. Forinstance, the reproducibility can be improved by cleaning the vaporizingtube 13 or the like during a period of a waiting time with a couple ofminutes between one substrate is processed and the nextCVD-thin-film-deposition process is performed with the next substratebeing put into the reaction chamber.

During the above cleaning process, the pressure of the carrier gas inthe pipe 3 is also monitored by the high-precision pressure gauge 17.Accordingly, a condition of the clogging of the orifice can bemonitored. As the cleaning process continued, the clogging of theorifice (atomizing nozzle) can be gradually eliminated since theprecipitated solutes are dissolved. Accordingly, the pressure of thecarrier gas is lowered. After the controller is notified by thehigh-precision pressure gauge 17 that the pressure of the carrier gas isturned less than or equal to the predetermined value (for instance, 100KPa) by receiving an output signal therefrom, the valves 6, 8 arere-opened so as to re-supply the raw-material solution.

Meanwhile, when the flow rate of one solution during the CVD process isXcc/min., it is preferable that the capacities of the pipes from thevalves 6 to 9 to the leading edges of the pipes 1, 2 be less than orequal to 8 Xcc, more preferably, less than or equal to 2 Xcc, andfurther preferably, less than or equal to Xcc.

Moreover, in this embodiment, the timing for the cleaning in order toeliminate the clogging of the atomizing nozzle with the solutions isdetermined by the high-precision pressure gauge 17 monitoring thepressure of the carrier gas, but not limited to this. For instance, thecleaning may be carried out by allowing the solutions and carrier gas toflow after predetermined times pass.

According to this embodiment, the orifice (atomizing nozzle) is cleanedby the solutions before it is completely clogged, and thus it can bebrought into an original condition. Therefore, the vaporizer for CVD canbe used for a significantly long time by performing the cleaning processduring the operation thereof. It takes approximately 10 hours fordisassembling the clogged vaporizer, cleaning and reassembling it. Theabove-described cleaning process, however, can be finished within acouple of minutes, and thus the operation time of the vaporizer can beconsiderably extended, while a production cost for a semiconductordevice or the like can be considerably reduced.

Moreover, in this embodiment, the first and second pipes 1, 2 areprovided adjacent to each other and in parallel with each other, whilethe pipe 3 for the carrier gas is provided outwardly relative to thefirst and second pipes 1, 2. Accordingly, the first raw-materialsolution (Sr[Ta(OEt)₅(OEtOMe)]₂) and the second raw-material solution(Bi(MMP)₃ can be separately supplied to the dispersing portion 14,whereby a chemical reaction of the first and second solutions insolution states does not occur, while the clogging in the inside of thepipe can be prevented. Therefore, the continuous operation time of thevaporizer for CVD can be extended.

Further, in this embodiment, the first and second pipes 1, 2 arecontained in the pipe 3 having a larger diameter, the carrier gas isallowed to flow a space in between the first, second pipes 1, 2 and thepipe 3, while the vaporizing tube 13 is provided on a downstream side ofthe flow. Since the pressurized carrier gas is allowed to flow the spacelocating the outsides of the pipes 1, 2 at a high speed, a temperaturerise in the first, second pipes 1, 2, the pipe 3 and the dispersingportion 14 can be suppressed. Accordingly, in the dispersing portion 14,a chemical reaction caused by the raw-material solutions can besuppressed since it is suppressed that only the solvents of theraw-material solutions vaporize, and thus the clogging of the dispersingportion 14 or the orifice can be suppressed. Therefore, the continuousoperation time of the vaporizer for CVD can be extended.

Still further, in this embodiment, the first and second raw-materialsolutions are dispersed in fine particulate or misty forms immediatelyafter mixed with the carrier gas by the dispersing portion 14 (within asingle second). It is thus suppressed that only the solvents of theraw-material solutions vaporize. Accordingly, in the dispersing portion14, a chemical reaction of the raw-material solutions by the dispersingportion 14 can be suppressed, and thus the clogging of the dispersingportion 14 or the orifice can be suppressed. Therefore, the continuousoperation time of the vaporizer for CVD can be extended.

Moreover, according to this embodiment, the first and secondraw-material solutions are dispersed by the dispersing portion 14, whilethe dispersed raw-material solutions in fine particulate or misty formsare heated in the inside of the vaporizing tube 13 so as to be vaporized(gasified) instantaneously. It is thus suppressed that only the solventof the raw-material solutions vaporizes. Accordingly, in the orifice orthe vaporizing tube 13 adjacent to the orifice, a chemical reaction ofthe raw-material solutions can be suppressed, and thus the clogging ofthe orifice or the vaporizing tube 13 can be suppressed. Therefore, thecontinuous operation time of the vaporizer for CVD can be extended.

As described, according to this embodiment, the clogging of the pipes 1to 3, the dispersing portion 14, the orifice and the vaporizing tube 13can be prevented, and even if they are clogged, the cleaning is carriedout for bringing them into the original conditions. Accordingly, thevaporizer for CVD can be continuously operated for long time. Therefore,a thin film of a ferroelectric material such as PZT, SBT or the like canbe deposited with good reproducibility and controllability, while thevaporizer and the solution-vaporization CVD of high performance can beembodied.

As described above, even if the high-precision pressure gauge 17 isprovided for monitoring the condition of the clogging, the cleaningprocess is required, and thus the vaporizer can not be completelycontinuously operated. Accordingly, when one reaction chamber isequipped with a plurality of vaporizers each having the cleaningmechanism, a solution-vaporization CVD apparatus which can continuouslydeposit over several hundred hours can be embodied. To be more precise,for instance, a reaction chamber is equipped with 12 vaporizers eachhaving the cleaning mechanism, and during the operation of thesolution-vaporization CVD apparatus, two vaporizers among them arecleaned, while other 10 vaporizers are continuously operated.Accordingly, a continuous operation of a solution-vaporization CVDapparatus over several hundred hours can be carried out, while adeposition rate of thin film can be remarkably improved. Thesolution-vaporization CVD apparatus, which sequentially cleans at leastone of the vaporizers so as to carry out a continuous deposition, issuitable for a case that, for instance, YBCO of a superconductive oxidethin film with a thickness of 10 μm is formed on a substrate having anextremely long tape shape.

Second Embodiment

FIG. 2C is a schematic view illustrating a structure of a solutionsupplying system included in a vaporizer for CVD according to a secondembodiment of the present invention. The same structure portions asthose illustrated in FIG. 1A will be denoted the same reference numbers,respectively, while detailed explanations thereof will be omitted.

The vaporizer for CVD illustrated in FIG. 2C has three pipes 1, 2 and 15for supplying three kinds of raw-material solutions, respectively. Thefirst pipe 1, the second pipe 2 and the third pipe 15 are providedadjacent to one another and in parallel with one another. The pipe 3 fora carrier gas is provided outwardly relative to the first to third pipes1, 2 and 15. The first to third pipes 1, 2 and 15 are inserted into theinside of the pipe 3, while the pipe 3 is formed in a manner containingthe first to third pipes 1, 2 and 15 thereinside.

A base end of the third pipe 15 is connected to a third supplyingmechanism (not illustrated) for supplying a chemical 3 and a solvent.The third supplying mechanism has a chemical-supplying-source forsupplying the chemical 3, and a solvent-supplying-source for supplyingthe solvent. A valve (not illustrated) and a mass-flow controller (notillustrated) are provided in between the chemical-supplying-source andthe third pipe 15. Moreover, a valve (not illustrated) and a mass-flowcontroller (not illustrated) are provided in between thesolvent-supplying-source and the third pipe 15. The solvent and thechemical 3 flow into each other (mix) in between thesolvent-supplying-source and the third pipe 15.

Leading ends of the first to third pipes 1, 2 and 15 are spaced awayfrom the orifice, respectively. A dispersing portion is formed inbetween the respective leading ends of the first to third pipes 1, 2 and15 in the inside of the pipe 3 and the orifice. The dispersing portionmixes: a first raw-material solution (one made by mixing the chemical 1and the solvent thereof) flows out of the leading end of the first pipe1; a second raw-material solution (one made by mixing the chemical 2 andthe solvent thereof) flows out of the leading end of the second pipe 2;a third raw-material solution (one made by mixing the chemical 3 and thesolvent thereof) flows out of the leading end of the third pipe 15; andthe argon or nitrogen gas flows out of the pipe 3, and then dispersesthe first to third raw-material solutions into the argon or nitrogen gasin fine particulate or misty forms.

According to the second embodiment, the same advantageous effect as thatof the first embodiment can be obtained.

Third Embodiment

FIG. 2D is a schematic view illustrating a structure of a solutionsupplying system included in a vaporizer for CVD according to a thirdembodiment of the present invention. The same structure portions asthose illustrated in FIG. 2C will be denoted the same reference numbers,respectively, while detailed explanations thereof will be omitted.

The vaporizer for CVD illustrated in FIG. 2D has four pipes 1, 2, 15 and16 for supplying four kinds of raw-material solutions. The first pipe 1,the second pipe 2, the third pipe 15 and the fourth pipe 16 are providedadjacent to one another and in parallel with one another. The pipe 3 fora carrier gas is provided outwardly relative to the first to fourthpipes 1, 2, 15 and 16. The first to fourth pipes 1, 2, 15 and 16 areinserted into the inside of the pipe 3, while the pipe 3 is formed in amanner containing the first to fourth pipes 1, 2, 15 and 16 thereinside.

A base end of the fourth pipe 16 is connected to a fourth supplyingmechanism (not illustrated) for supplying a chemical 4 and a solvent.The fourth supplying mechanism has a chemical-supplying-source forsupplying the chemical 4, and a solvent-supplying-source for supplyingthe solvent. A valve (not illustrated) and a mass-flow controller (notillustrated) are provided in between the chemical-supplying-source andthe fourth pipe 16. Moreover, a valve (not illustrated) and a mass-flowcontroller (not illustrated) are provided in between thesolvent-supplying-source and the fourth pipe 16. The solvent and thechemical 4 flow into each other (mix) in between thesolvent-supplying-source and the fourth pipe 16.

Leading ends of the first to fourth pipes 1, 2, 15 and 16 are spacedaway from the orifice, respectively. A dispersing portion is formed inbetween the respective leading ends of the first to fourth pipes 1, 2,15 and 16 in the inside of the pipe 3 and the orifice. The dispersingportion mixes: a first raw-material solution (one made by mixing thechemical 1 and the solvent thereof) flows out of the leading end of thefirst pipe 1; a second raw-material solution (one made by mixing thechemical 2 and the solvent thereof) flows out of the leading end of thesecond pipe 2; a third raw-material solution (one made by mixing thechemical 3 and the solvent thereof) flows out of the leading end of thethird pipe 15; a fourth raw-material solution (one made by mixing thechemical 4 and the solvent thereof) flows out of the leading end of thefourth pipe 16; and the argon or nitrogen gas flows out of the pipe 3,and then disperses the first to fourth raw-material solutions in theargon or nitrogen gas in fine particulate or misty forms.

According to the third embodiment, the same advantageous effect as thatof the second embodiment can be obtained.

The present invention is not limited to the above embodiments, variousembodiments and changes may be made thereonto without departing from thebroad spirit and scope of the invention. For instance, the vaporizer,the vaporization method for CVD and the CVD apparatus according to thepresent invention can be applied variously, not only they are applied tothe formation of a high-quality ferroelectric thin film (for instance,SBT, PZT) for a FeRAM-LSI as a ferroelectric memory, but also theformation of other films such as YBCO (super conductive oxide), thickPZT/PLZT/SBT film(for filter, MEMS, optical interconnect, HD), metalfilm (Ir, Pt, Cu), barrier metal (TiN, TaN), high k film(HfOx, Al₂O₃,BST or the like) with various kinds of chemicals used, for instance, amaterial having low vapor pressure.

Moreover, in the above embodiments, the first raw-material solution ismade by dissolving Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ in the solution thereof,while the second raw-material solution is made by dissolving Bi(MMP)₃ inthe solution thereof, but the raw-material solution is not limited tothose. For instance, a raw-material solution may be made by dissolvingthe other kind of a solid material in a solution thereof. Further, aliquid material of Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ or the like itself may beused as a raw-material solution, while one made by mixing a liquidmaterial with a solution may be used.

Further, in the above embodiments, one kind of a thin film is formed ona substrate to be processed, respectively. However, plural kinds of thinfilms may be successively formed on a substrate. To be more precise, araw-material solution and a carrier gas are allowed to flow into thereaction chamber (CVD chamber) via the vaporizing tube for CVD for anappropriate period so as to form a first thin film on a substrate. Next,a valve for the raw-material solution is changed to be as an exhaust,while another kind of raw-material solution is supplied to the reactionchamber via the vaporizing tube at a predetermined flow rate. When a sumof the flow rate of this raw-material solution (that is, volume thereof)exceeds one to five times of a capacity of a pipe from the valve to thereaction chamber, this raw-material solution and a carrier gas areallowed to flow into the reaction chamber via the vaporizing tube for anappropriate period so as to form a second thin film on the substrate.Accordingly, two kinds of thin films having different compositions canbe successively formed. Moreover, by repeating this process, three ormore kinds of thin films can be formed. Meanwhile, when supplyinganother kind of raw-material solution to the reaction chamber, atemperature of the substrate and a pressure when reacting may beappropriately changed.

EXAMPLE

An example according to the present invention will now be explained.

Resultants of monitoring the pressures of the carrier gas areillustrated in FIGS. 3 to 8. As illustrated in FIG. 3, at a monitorpoint 80, when chemicals were started to flow into the vaporizing tube13, the pressure of the carrier gas gradually increased. At a monitorpoint 420, the pressure of the BiMMP carrier gas reached to 220 kPa(approximately 2.2 barometric pressure (gage pressure)). At this point,the supply of BiMMP (0.2 ccm) was terminated, while a cleaning solventECH (0.5 ccm) was allowed to flow. Accordingly, the pressure of thecarrier gas rapidly fell and stabilized at a monitor point 440. Thepressure-fall thereof indicated that BiMMP adhered to the atomizingnozzle (orifice) was eliminated.

As illustrated in FIGS. 4 to 6, similar to the case of FIG. 3, thephenomenon of the adhesion with respect to the atomizing nozzle occurredwith good reproducibility. The phenomenon was observed not only in aSBT-CVD process with Sr[Ta(OEt)₅(OC₂H₄OMe)]₂ and Bi(MMP)₃ used, but alsoin other SBT-CVD processes with the following chemicals used:Pb(DPM)₂/ECH (0.15 mol/L); Zr(DIBM)₄/ECH (0.15 mol/L); andTi(Oi-Pr)₂(DPM)₂/ECH (0.30 mol/L).

In the case illustrated in FIG. 8, a change of the pressure in thecarrier gas was small. Because the densities of the solutions ofSr[Ta(OEt)₅(OC₂H₄OMe)]₂ and Bi(MMP)₃ were diluted by ½, the progress ofthe clogging at the atomizing nozzle was declined. In this case, apressure increase in the carrier gas was not observed during anapproximately 40 minute SBT thin film deposition. Moreover, byperforming a cleaning process with respect to each deposition, a SBT-CVDprocess was carried out in a condition that no clogging occurred

FIGS. 9 and 10 illustrate resultants of a reproducibility experiment ofSBT-CVD with the vaporizer of the present invention used.

FIG. 9 illustrates reproducibility of deposition rate. A deposition-rateexperiment with 100 batches was performed, while the average depositionrate was 7.29 nm/min., σ=0.148 nm/min., and thus a good continuousdeposition and a good reproducibility were achieved.

FIG. 10 illustrates reproducibility of film composition. Adeposition-rate experiment with 100 batches was performed, while theaverage relative proportion of Bi/Sr was 3.08, σ=0.065, and thus thegood reproducibility was achieved. Moreover, the average relativeproportion of Ta/Sr was 2.07, σ=0.0166, and thus a good continuousdeposition was achieved.

1-14. (canceled)
 15. A vaporizer for CVD comprising: a dispersingportion dispersing a plurality of raw-material solutions in a carriergas in fine particulate or misty forms; a plurality of paths for theplurality of raw-material solutions, each of said plurality of pathssupplying the plurality of raw-material solutions to said dispersingportion separately from one another; a path for the carrier gas, saidpath supplying the carrier gas to said dispersing portion separatelyfrom the plurality of raw-material solutions; a vaporizing membervaporizing the plurality of raw-material solutions dispersed by saiddispersing portion; an orifice connected to said vaporizing member andsaid dispersing portion, said orifice introducing the plurality ofraw-material solutions dispersed by said dispersing portion into saidvaporizing member; and a cleaning mechanism cleaning at least one ofsaid dispersing portion, said orifice and said vaporizing member. 16.The vaporizer for CVD according to claim 15, further comprising areaction chamber connected to said vaporizer to form asolution-vaporization CVD apparatus.
 17. The vaporizer for CVD accordingto claim 15, further comprising a monitoring mechanism for monitoring apressure of the carrier gas.
 18. The vaporizer for CVD according toclaim 17, further comprising a reaction chamber connected to saidvaporizer to form a solution-vaporization CVD apparatus.
 19. A vaporizerfor CVD comprising: a dispersing portion dispersing a plurality ofraw-material solutions in a carrier gas in fine particulate or mistyforms; a plurality of paths for the plurality of raw-material solutions,each of said plurality of paths supplying the plurality of raw-materialsolutions to said dispersing portion separately from one another; a pathfor the carrier gas, said path supplying the carrier gas to saiddispersing portion separately from the plurality of raw-materialsolutions; a monitoring mechanism for monitoring a pressure of thecarrier gas; a vaporizing member vaporizing the plurality ofraw-material solutions dispersed by said dispersing portion; and anorifice connected to said vaporizing member and said dispersing portion,said orifice introducing the plurality of raw-material solutionsdispersed by said dispersing portion into said vaporizing member. 20.The vaporizer for CVD according to claim 19, further comprising areaction chamber connected to said vaporizer to form asolution-vaporization CVD apparatus.
 21. A vaporizer for CVD comprising:a plurality of pipes for a plurality of raw-material solutions, each ofsaid plurality of pipes supplying the plurality of raw-materialsolutions separately from one another; a pipe for a carrier gas, saidpipe being provided in a manner covering outwards of said plurality ofpipes, while said pipe allowing the carrier gas, said carrier gas beingpressurized, to flow thereinside and the outward of each of saidplurality of pipes; an orifice provided on a leading end of said pipefor the carrier gas, said orifice being spaced away from leading ends ofsaid plurality of pipes for the plurality of raw-material solutions; avaporizing tube connected to said leading end of said pipe for thecarrier gas, said vaporizing tube being connected to the inside of saidpipe for the carrier gas via said orifice; a cleaning mechanism cleaningat least one of said leading end of said pipe for the carrier gas, saidorifice, said vaporizing tube; and a heating means for heating saidvaporizing tube.
 22. The vaporizer for CVD according to claim 21,further comprising a reaction chamber connected to said vaporizer toform a solution-vaporization CVD apparatus.
 23. The vaporizer for CVDaccording to claim 22, wherein a deposition is carried out with theplurality of raw-material solutions used, the plurality of raw-materialsolutions being vaporized by said vaporizing tube.
 24. Thesolution-vaporization CVD apparatus according to claim 23, wherein: thesolution-vaporization CVD apparatus is equipped with a plurality ofvaporizers for CVD; and some of said plurality of vaporizers for CVD arerespectively in a cleaned condition cleaned by said cleaning mechanism,while others thereof are respectively in operated conditions; and theplurality of vaporized raw-material solutions are continuously suppliedto said reaction chamber by swapping said plurality of vaporizers forCVD in the operated conditions for those in the cleaned conditions astime advances.
 25. The vaporizer for CVD according to claim 21, furthercomprising a monitoring mechanism for monitoring a pressure of thecarrier gas in an inside of said pipe for the carrier gas.
 26. Thevaporizer for CVD according to claim 25, wherein said cleaning mechanismcleans said leading end of said pipe for the carrier gas and saidorifice by supplying at least a solution thereto.
 27. The vaporizer forCVD according to claim 26, further comprising a reaction chamberconnected to said vaporizer to form a solution-vaporization CVDapparatus, and wherein a deposition is carried out with the plurality ofraw-material solutions used, the plurality of raw-material solutionsbeing vaporized by said vaporizing tube.
 28. The solution-vaporizationCVD apparatus according to claim 27, wherein: the solution-vaporizationCVD apparatus is equipped with a plurality of vaporizers for CVD; andsome of said plurality of vaporizers for CVD are respectively in acleaned condition cleaned by said cleaning mechanism, while othersthereof are respectively in operated conditions; and the plurality ofvaporized raw-material solutions are continuously supplied to saidreaction chamber by swapping said plurality of vaporizers for CVD in theoperated conditions for those in the cleaned conditions as timeadvances.
 29. The vaporizer for CVD according to claim 25, furthercomprising a reaction chamber connected to said vaporizer to form asolution-vaporization CVD apparatus.
 30. The vaporizer for CVD accordingto claim 29, further comprising a reaction chamber connected to saidvaporizer to form a solution-vaporization CVD apparatus, and wherein adeposition is carried out with the plurality of raw-material solutionsused, the plurality of raw-material solutions being vaporized by saidvaporizing tube.
 31. The solution-vaporization CVD apparatus accordingto claim 30 wherein: the solution-vaporization CVD apparatus is equippedwith a plurality of vaporizers for CVD; and some of said plurality ofvaporizers for CVD are respectively in a cleaned condition cleaned bysaid cleaning mechanism, while others thereof are respectively inoperated conditions; and the plurality of vaporized raw-materialsolutions are continuously supplied to said reaction chamber by swappingsaid plurality of vaporizers for CVD in the operated conditions forthose in the cleaned conditions as time advances.
 32. The vaporizer forCVD according to claim 21, wherein said cleaning mechanism cleans saidleading end of said pipe for the carrier gas and said orifice bysupplying at least a solution thereto.
 33. The vaporizer for CVDaccording to claim 32, further comprising a reaction chamber connectedto said vaporizer to form a solution-vaporization CVD apparatus.
 34. Thevaporizer for CVD according to claim 33, wherein a deposition is carriedout with the plurality of raw-material solutions used, the plurality ofraw-material solutions being vaporized by said vaporizing tube.
 35. Thesolution-vaporization CVD apparatus according to claim 34, wherein: thesolution-vaporization CVD apparatus is equipped with a plurality ofvaporizers for CVD; and some of said plurality of vaporizers for CVD arerespectively in a cleaned condition cleaned by said cleaning mechanism,while others thereof are respectively in operated conditions; and theplurality of vaporized raw-material solutions are continuously suppliedto said reaction chamber by swapping said plurality of vaporizers forCVD in the operated conditions for those in the cleaned conditions astime advances.
 36. A vaporization method for CVD comprising: supplying aplurality of raw-material solutions and a carrier gas to a dispersingportion separately from one another; mixing the plurality ofraw-material solutions and the carrier gas by the dispersing portion anddispersing the plurality of raw-material solutions in the carrier gas infine particulate or misty forms; vaporizing the raw-material solutionsby adiabatic expansion immediately after dispersing; and cleaning atleast one of the dispersing portion and an area for vaporizing theraw-material solutions.
 37. A vaporization method for CVD, comprising:supplying a plurality of raw-material solutions and a carrier gas to adispersing portion separately from one another; mixing the plurality ofraw-material solutions and the carrier gas by the dispersing portion,and dispersing the plurality of raw-material solutions in the carriergas in fine particulate or misty forms; vaporizing the raw-materialsolutions by adiabatic expansion immediately after dispersing;monitoring a pressure of the carrier gas while vaporizing theraw-material solutions, and terminating the supply of the raw-materialsolutions to the dispersing portion upon observing that the pressure ofthe carrier gas exceeds a predetermined value; and cleaning at least oneof the dispersing portion and an area for vaporizing the plurality ofraw-material solutions.
 38. The vaporization method for CVD according toclaim 37, wherein a solvent for cleaning and solvents contained in theplurality of raw-material solutions are homogeneous.
 39. Thevaporization method for CVD according to claim 38, wherein: said processfor cleaning is one for cleaning at least one of the dispersing portionand the area for vaporizing the plurality of raw-material solutions bysupplying a solvent and the carrier gas thereto; and the pressure of thecarrier gas is monitored during said process for cleaning so that thesupply of the solvent is terminated upon observing that the pressure ofthe carrier gas is turned less than or equal to the predetermined valueso as to terminate said process for cleaning.
 40. The vaporizationmethod for CVD according to claim 37, wherein a solvent for cleaning andsolvents contained in the plurality of raw-material solutions arehomogeneous.